Detection of low noise frequencies for multiple frequency sensor panel stimulation
First Claim
1. A method for determining low noise stimulation frequencies for use in generating an image of touch from a touch sensor panel, comprising:
- while applying no stimulation frequency to any of a plurality of drive lines in the touch sensor panel, receiving a noise signal from each of a plurality of sense lines in the touch sensor panel into a charge amplifier of a different sense channel;
summing an output of all charge amplifiers to generate a combined noise signal;
demodulating the combined noise signal with in-phase (I) and quadrature (Q) components of a first plurality of frequencies;
for each of the first plurality of frequencies, accumulating the I and Q components of the demodulated noise signal and generating a noise value for that frequency by calculating a magnitude of the accumulated I and Q components of the demodulated noise signal; and
determining the low noise frequencies by selecting those frequencies whose generated noise values are smallest.
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Accused Products
Abstract
The identification of low noise stimulation frequencies for detecting and localizing touch events on a touch sensor panel is disclosed. Each of a plurality of sense channels can be coupled to a separate sense line in a touch sensor panel and can have multiple mixers, each mixer using a demodulation frequency of a particular frequency, phase and delay. With no stimulation signal applied to any drive lines in the touch sensor panel, pairs of mixers can demodulate the sum of the output of all sense channels using the in-phase (I) and quadrature (Q) signals of a particular frequency. The demodulated outputs of each mixer pair can be used to calculate the magnitude of the noise at that particular frequency, wherein the lower the magnitude, the lower the noise at that frequency. Several low noise frequencies can be selected for use in a subsequent touch sensor panel scan function.
179 Citations
28 Claims
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1. A method for determining low noise stimulation frequencies for use in generating an image of touch from a touch sensor panel, comprising:
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while applying no stimulation frequency to any of a plurality of drive lines in the touch sensor panel, receiving a noise signal from each of a plurality of sense lines in the touch sensor panel into a charge amplifier of a different sense channel; summing an output of all charge amplifiers to generate a combined noise signal; demodulating the combined noise signal with in-phase (I) and quadrature (Q) components of a first plurality of frequencies; for each of the first plurality of frequencies, accumulating the I and Q components of the demodulated noise signal and generating a noise value for that frequency by calculating a magnitude of the accumulated I and Q components of the demodulated noise signal; and determining the low noise frequencies by selecting those frequencies whose generated noise values are smallest. - View Dependent Claims (2, 3)
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4. A method for determining low noise stimulation frequencies for use in generating an image of touch from a touch sensor panel, comprising:
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demodulating a combined noise signal from all sense lines in an unstimulated touch sensor panel with in-phase (I) and quadrature (Q) components of a first plurality of frequencies; accumulating the I and Q components of the demodulated noise signal for each of the first plurality of frequencies; calculating a magnitude of the accumulated I and Q components of the demodulated noise signal for each of the first plurality of frequencies; and determining the low noise frequencies by selecting those frequencies whose generated magnitudes are smallest. - View Dependent Claims (5, 6)
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7. An apparatus for determining low noise stimulation frequencies for use in generating an image of touch from a touch sensor panel, comprising:
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a plurality of sense channels, each sense channel including a charge amplifier configured for receiving a signal from a different sense line of the touch sensor panel, a plurality of mixers coupled for receiving a sum of all charge amplifiers in all sense channels, one frequency generator circuit coupled to each of the plurality of mixers for generating a demodulation frequency, and one accumulator coupled to each of the plurality of mixers for generating an accumulated mixer output; a summing circuit coupled for receiving an output of each charge amplifier in each sense channel and generating the sum of all charge amplifiers in all sense channels; and a plurality of magnitude calculator circuits, each magnitude calculator circuit coupled for receiving the accumulated mixer output from a pair accumulators, each pair of accumulators coupled to two mixers being demodulated with in-phase (I) and quadrature (Q) components of a particular demodulation frequency, each magnitude calculator circuit generating a magnitude value corresponding to an amount of noise at that frequency. - View Dependent Claims (8, 9, 10, 11, 12)
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13. An apparatus for determining low noise stimulation frequencies for use in generating an image of touch from a touch sensor panel, comprising:
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a summing circuit coupled for receiving a noise signal from each of a plurality of sense lines in the touch sensor panel and generating a combined noise signal; a plurality of pairs of mixers, each pair of mixers for demodulating the combined noise signal with in-phase (I) and quadrature (Q) components of a particular demodulation frequency; one accumulator coupled to each of the plurality of mixers for generating an accumulated mixer output; and a plurality of magnitude calculator circuits, each magnitude calculator circuit coupled for receiving the accumulated mixer outputs from a particular pair accumulators associated with a particular pair of mixers, each magnitude calculator circuit generating a magnitude value corresponding to an amount of noise at the demodulation frequency for the particular pair of mixers. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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20. A mobile telephone including an apparatus for determining low noise stimulation frequencies for use in generating an image of touch from a touch sensor panel, the apparatus comprising:
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a summing circuit coupled for receiving a noise signal from each of a plurality of sense lines in the touch sensor panel and generating a combined noise signal; a plurality of pairs of mixers, each pair of mixers for demodulating the combined noise signal with in-phase (I) and quadrature (Q) components of a particular demodulation frequency; one accumulator coupled to each of the plurality of mixers for generating an accumulated mixer output; and a plurality of magnitude calculator circuits, each magnitude calculator circuit coupled for receiving the accumulated mixer outputs from a particular pair accumulators associated with a particular pair of mixers, each magnitude calculator circuit generating a magnitude value corresponding to an amount of noise at the demodulation frequency for the particular pair of mixers.
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21. A digital audio player including an apparatus for determining low noise stimulation frequencies for use in generating an image of touch from a touch sensor panel, the apparatus comprising:
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a summing circuit coupled for receiving a noise signal from each of a plurality of sense lines in the touch sensor panel and generating a combined noise signal; a plurality of pairs of mixers, each pair of mixers for demodulating the combined noise signal with in-phase (I) and quadrature (Q) components of a particular demodulation frequency; one accumulator coupled to each of the plurality of mixers for generating an accumulated mixer output; and a plurality of magnitude calculator circuits, each magnitude calculator circuit coupled for receiving the accumulated mixer outputs from a particular pair accumulators associated with a particular pair of mixers, each magnitude calculator circuit generating a magnitude value corresponding to an amount of noise at the demodulation frequency for the particular pair of mixers.
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22. A method for operating a touchscreen, the touchscreen having a touch sensor panel and a display device, the method comprising:
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updating the display device during an active period of the display device; and determining low noise stimulation frequencies for use in generating an image of touch from a touch sensor panel during a vertical blanking phase of the display device. - View Dependent Claims (23)
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24. An apparatus for selectively determining low noise stimulation frequencies or obtaining an image of touch from a touch sensor panel, comprising:
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a plurality of sense channels, each sense channel including a charge amplifier configured for receiving a signal from a different sense line of the touch sensor panel, a multiplexer having a first input coupled to an output of the charge amplifier, a plurality of mixers coupled to an output of the multiplexer, one frequency generator circuit coupled to each of the plurality of mixers for generating a demodulation frequency, and one accumulator coupled to each of the plurality of mixers for generating an accumulated mixer output; a summing circuit coupled for receiving an output of each charge amplifier in each sense channel, the summing circuit generating an output coupled to a second input of the multiplexer in each sense channel; and a plurality of magnitude and phase calculator circuits, each magnitude and phase calculator circuit coupled to two accumulators. - View Dependent Claims (25, 26, 27)
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28. A method for selectively determining low noise stimulation frequencies or obtaining an image of touch from a touch sensor panel, comprising:
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receiving each of a plurality of sense lines on the touch sensor panel into a charge amplifier of a separate sense channel; when determining low noise stimulation frequencies, providing no stimulus to any of a plurality of drive lines for the touch sensor panel, demodulating a sum of all charge amplifiers in all sense channels with in-phase (I) and quadrature (Q) components of a first plurality of frequencies, generating a value representing a noise level of each of the first plurality of frequencies by calculating a magnitude of the I and Q components of each frequency, and determining a second plurality of low noise frequencies by selecting those frequencies whose generated noise level values are smallest; and when obtaining the image of touch from the touch sensor panel, for each sense channel, demodulating an output of the charge amplifier in that sense channel with each of the second plurality of frequencies, accumulating the demodulated signals to generate a plurality of accumulated demodulated signals, and storing the plurality of accumulated demodulated signals.
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Specification